Antigen-specific inhibition of CD4+ T-cell responses to beta-lactoglobulin by its single amino acid-substituted mutant form through T-cell receptor antagonism.
T-cell responses can be antagonized by some single amino acid-substituted analogs of a peptide ligand for T-cell receptors (TCR), and these are called TCR antagonists. In this study, we addressed the question of whether TCR antagonism can be elicited by a whole protein antigen carrying a mutated T-cell determinant region corresponding to a TCR antagonist peptide. To clarify this, we examined the ability of a single amino acid-substituted mutant form of bovine beta-lactoglobulin (beta-Lg) to inhibit three CD4+ T-cell clones recognizing a peptide corresponding to an immunodominant determinant region 119-133 of beta-Lg (p119-133). First, we identified pD129A, an analog of p119-133 with a substitution of Ala for 129Asp, as an antagonist which can inhibit the response of two of the three T-cell clones. Then, using a yeast expression system, we prepared a mutant beta-Lg (mutD129A) with the same substitution of Ala for 129Asp as that in pD129A. This mutant protein could inhibit the proliferation of the two T-cell clones in a manner similar to the effect of pD129A. From these results we can demonstrate that TCR antagonism can be elicited by peptides naturally processed from a single-substituted mutant protein as well as by the corresponding peptides added exogenously.
Totsuka
M
M
Department of Applied Biological Chemistry, University of Tokyo, Japan. atotuka@hongo.ecc.U-tokyo.ac.jp
Furukawa
S
S
Sato
E
E
Ametani
A
A
Kaminogawa
S
S
D000409:Alanine / Q000235:genetics / Q000276:immunology; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D001224:Aspartic Acid / Q000235:genetics / Q000276:immunology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D002417:Cattle; D002999:Clone Cells; D005260:Female; D007782:Lactoglobulins / Q000235:genetics* / Q000276:immunology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010455:Peptides / Q000235:genetics / Q000276:immunology; D011948:Receptors, Antigen, T-Cell / Q000037:antagonists & inhibitors / Q000276:immunology*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000276:immunology
D007782:Lactoglobulins; D010455:Peptides; D011948:Receptors, Antigen, T-Cell; D011993:Recombinant Fusion Proteins; D001224:Aspartic Acid; D000409:Alanine